1. Field of the Invention
The present invention relates to a process for locating the depth downhole of a lost return zone. The location of the depth down an open borehole, where the surrounding strata has collapsed, and is created what is referred to as a lost return zone.
2. General Background
In the drilling of oil wells, the manner in which the drill bit is maintained relatively cool, and the cuttings from the bit are returned to the surface is very important. In the present state of the art, as the bit is drilling through the strata downhole, a particular weight mud, either water base or oil base, is circulated down through the drill string through the drill bit, wherein the mud picks up the cuttings from the bit, and is recirculated back to the surface in the annular space between the outer wall of the drill string and the wall of the formation that the bit is drilling through. The column of mud, in accomplishing this constant circulation down through the string and up through the annulus, also serves to protect against the inadvertent striking of a pocket of pressurized hydrocarbons, and to maintain the hydrostatic head on the formation so that the well would not blow out in the event that such a pocket were struck by the drill bit.
However, one problem which is confronted in open hole drilling, is the fact that often times the drill bit will run through a zone of formation which is called a "no circulation zone", where the wall of the formation would collapse, and allow the mud in the annulus to flow into the formation, and into the lost circulation zone. Through experience, it has been found when such lost circulation occurs, there are few remedies that can be achieved in order to regain circulation. If, for example, one knows of the depth of the lost circulation zone, it may be possible to send materials down the annulus to that particular depth, in order to "plug" the hole in the formation, and maintain the drilling process. Otherwise, often times it is necessary that this particular wall of the annulus has to be cemented so as to provide the necessary wall that will not allow further loss of mud so that recirculation of the mud can be obtained. However, if one is unable to determine the depth of the lost circulation zone, then there is virtually no way that recirculation of the mud can be obtained, and often times the hole must be cemented up and redrilled at a considerable loss in time and money.
Therefore, there is a need for one having the ability to calculate the depth of the lost circulation zone, so that the zone may be plugged or unnecessary work done on the wall of the annulus in order to restructure the wall so that mud can be circulated through the drill pipe and up to the annulus.